pthread_sigmask.c 2.72 KB
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/* POSIX compatible signal blocking for threads.
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   Copyright (C) 2011-2019 Free Software Foundation, Inc.
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   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
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   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
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#include <config.h>

/* Specification.  */
#include <signal.h>

#include <errno.h>
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#include <stddef.h>

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#if PTHREAD_SIGMASK_INEFFECTIVE
# include <string.h>
#endif

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#if PTHREAD_SIGMASK_UNBLOCK_BUG
# include <unistd.h>
#endif
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int
pthread_sigmask (int how, const sigset_t *new_mask, sigset_t *old_mask)
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#undef pthread_sigmask
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{
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#if HAVE_PTHREAD_SIGMASK
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  int ret;

# if PTHREAD_SIGMASK_INEFFECTIVE
  sigset_t omask, omask_copy;
  sigset_t *old_mask_ptr = &omask;
  sigemptyset (&omask);
  /* Add a signal unlikely to be blocked, so that OMASK_COPY
     is unlikely to match the actual mask.  */
  sigaddset (&omask, SIGILL);
  memcpy (&omask_copy, &omask, sizeof omask);
# else
  sigset_t *old_mask_ptr = old_mask;
# endif

  ret = pthread_sigmask (how, new_mask, old_mask_ptr);

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# if PTHREAD_SIGMASK_INEFFECTIVE
  if (ret == 0)
    {
      /* Detect whether pthread_sigmask is currently ineffective.
         Don't cache the information: libpthread.so could be dynamically
         loaded after the program started and after pthread_sigmask was
         called for the first time.  */
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      if (memcmp (&omask_copy, &omask, sizeof omask) == 0
          && pthread_sigmask (1729, &omask_copy, NULL) == 0)
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        {
          /* pthread_sigmask is currently ineffective.  The program is not
             linked to -lpthread.  So use sigprocmask instead.  */
          return (sigprocmask (how, new_mask, old_mask) < 0 ? errno : 0);
        }
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      if (old_mask)
        memcpy (old_mask, &omask, sizeof omask);
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    }
# endif
# if PTHREAD_SIGMASK_FAILS_WITH_ERRNO
  if (ret == -1)
    return errno;
# endif
# if PTHREAD_SIGMASK_UNBLOCK_BUG
  if (ret == 0
      && new_mask != NULL
      && (how == SIG_UNBLOCK || how == SIG_SETMASK))
    {
      /* Give the OS the opportunity to raise signals that were pending before
         the pthread_sigmask call and have now been unblocked.  */
      usleep (1);
    }
# endif
  return ret;
#else
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  int ret = sigprocmask (how, new_mask, old_mask);
  return (ret < 0 ? errno : 0);
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#endif
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}